Proposed resolution (approved by CWG 2024-03-20):

1. Append to 6.7.5.1 [basic.stc.general] paragraph 1:

   [ Note: After the duration of a region of storage has ended, the use of pointers to that region of storage is limited (6.8.4 [basic.compound]). -- end note ]

2. Remove 6.7.5.1 [basic.stc.general] paragraph 4 as follows:

   When the end of the duration of a region of storage is reached, the values of all pointers representing the address of any part of that region of storage become invalid pointer values (6.8.4 [basic.compound]). Indirection through an invalid pointer value and passing an invalid pointer value to a deallocation function have undefined behavior. Any other use of an invalid pointer value has implementation-defined behavior. [ Footnote: ... ]

3. Change in 6.8.4 [basic.compound] paragraph 3 as follows:

   [Note 2: A pointer past the end of an object (7.6.6 [expr.add]) is not considered to point to an unrelated object of the object's type, even if the unrelated object is located at that address. A pointer value becomes invalid when the storage it denotes reaches the end of its storage duration; see 6.7.5 [basic.stc]. —end note]

4. Insert a new paragraph after 6.8.4 [basic.compound] paragraph 3:

   A pointer value P is valid in the context of an evaluation E if P is a null pointer value, or if it is a pointer to or past the end of an object O and E happens before the end of the duration of the region of storage for O. If a pointer value P is used in an evaluation E and P is not valid in the context of E, then the behavior is undefined if E is an indirection (7.6.2.2 [expr.unary.op]) or an invocation of a deallocation function (6.7.5.5.3 [basic.stc.dynamic.deallocation]), and implementation-defined otherwise. [ Footnote: Some implementations might define that copying such a pointer value causes a system-generated runtime fault. -- end footnote ] [ Note: P can be valid in the context of E even if it points to a type unrelated to that of O or if O is not within its lifetime, although further restrictions apply to such pointer values (6.7.3 [basic.life], 7.2.1 [basic.lval], 7.6.6 [expr.add]). —end note]

5. Change in 7.6.1.9 [expr.static.cast] paragraph 14 as follows:

   ... If the original pointer value represents the address A of a byte in memory and A does not satisfy the alignment requirement of T, then the resulting pointer value (6.8.4 [basic.compound]) is unspecified. ...

6. Change in 7.6.1.10 [expr.reinterpret.cast] paragraph 5 as follows:

   A value of integral type or enumeration type can be explicitly converted to a pointer. A pointer converted to an integer of sufficient size (if any such exists on the implementation) and back to the same pointer type will have its original value (6.8.4 [basic.compound]); mappings between pointers and integers are otherwise implementation-defined.

[Accepted as a DR at the March, 2024 meeting.]

Subclause 6.7.5.1 [basic.stc.general] paragraph 4 seems to suggest that the end of duration of a region of storage causes actual modifications to pointer objects, causing questions about data races (in the abstract machine).